The overall objective of this project is the understanding of the relationship between chemical structure and metabolic function of insulin with special emphasis on the delineation of the amino acid residues or structural entities involved in the binding of insulin on its receptor ("binding region") and those residues or functional groups which are involved in the expression of the hormone's physiological activities "message region." The specific aims include: (1) The synthesis of insulin analogs bearing side chain modifications of amino acid residues found in the A and B chains of the molecule and determination of the effects of these modifications on the conformation, biological activity and receptor binding affinity of these analogs; (2) The synthesis of insulin analogs in which particular peptide bonds of the backbone have been substituted by bonds incapable of participating in putative hydrogen bonding with the receptor, and determination of the effects these modifications have on the conformation and the biological profile of these analogs; (3) The synthesis of insulin analogs incorporating those structural features of Insulin-like Growth Factor (IGF) which are puntatively responsible for binding to IGF receptors and determination of the effects of these modifications on the growth-stimulating properties of these analogs. These latter modifications may lead to "new insulins" with enhanced mitogenic properties. In this regard, the synergistic effect of vasopressin in insulin-stimulated mitogenesis in 3T3 cell line will be investigated by the synthesis and biological evaluation of a complex molecule consisting of insulin covalently bound to vasopressin; (4) The synthesis of an insulin analog in which the B16-B17 peptide bond, which appears to be the initial site of insulin degradation by insulin protease, will be substituted with an enzyme-resistant bond. This may lead to insulin analog with higher potency and/or longer duration of action than the natural hormone.